Three-dimensional (3D) printing refers to processes that create 3D objects based upon digital 3D object models and a materials dispenser. In 3D printing, a dispenser moves in at least 2-dimensions and dispenses material according to a determined print pattern. To build a 3D object, a platform that holds the object being printed is adjusted such that the dispenser is able to apply many layers of material, and printing many layers of material, one layer at a time, may print a 3D object.
A conventionally known 3D printing process is the UV ink-jet process. It is a three-stage process of applying a material, printing a UV-curable liquid, and finally hardened using a UV source. These steps are repeated layer-by-layer. In conventional 3D printing, disclosed in U.S. Pat. Nos. 6,375,874 and 6,416,850, generally an inkjet type print head delivers a liquid or a colloidal binder material to layers of a powdered build material. The printing technique involves applying a layer of a powdered build material to a surface typically using a roller. After the build material is applied to the surface, the print head delivers the liquid binder to predetermined areas of the layer of material. The binder infiltrates the material and reacts with the powder, causing the layer to solidify in the printed areas by, for example, activating an adhesive in the powder. The binder also penetrates into the underlying layers, producing interlayer bonding. After the first cross-sectional portion is formed, the previous steps are repeated, building successive cross-sectional portions until the final object is formed.
The oldest and the best-known laser-based 3D printing process is stereolithography (SLA). In this process, a liquid composition of a radiation-curable polymer is hardened layer-by-layer by using a laser. A similar process is Selective Laser Sintering (SLS) in which a thermoplastic or a sinterable metal is sintered selectively layer-by-layer by a laser to form the 3D object.
U.S. Pat. No. 5,121,329 describes the fused deposition modeling (FDM) process for the production of three-dimensional objects using an extrusion-based, digital manufacturing system. There are also other known processes that are substantially analogous with slight differences, for example fused filament fabrication (FFF), melt extrusion manufacturing (MEM) or selective deposition modeling (SDM).
In the FDM method, two different polymer filaments are melted in a nozzle and are printed selectively. One of the materials involves a support material, which is needed only at locations above which an overhanging part of the 3D object is printed and requires support during the subsequent printing procedure. The support material can be removed subsequently, e.g. via dissolution in acids, bases or water. The other material (the build material) forms the actual 3D object. Here again, the print is generally achieved layer-by-layer.